1Caption: This boulder is made of many rocks stuck together.2 Have you ever looked closely at rocks? They come in many colors, shapes, and sizes. Some rocks are very hard. Some are easily broken. Some rocks are smooth. Others are very rough. There are many different kinds of rocks, but all rocks can be placed in one of three groups. Rocks are put into groups based on how they were formed. There are only three ways that rocks can be made. One kind of rock is sedimentary rock. It is formed very slowly. It is made from tiny pieces of older rock, sand, minerals, and fossils, called sediments. Sediments are laid on the ground by water, .....For the complete story with questions: click here for printable